#define _CRT_SECURE_NO_WARNINGS 1
#include <stdio.h>

int main()
{
    float a = 0, b = 0, c = 0, d = 0, e = 0, sum = 0;
    scanf("%f %f %f %f %f", &a, &b, &c, &d, &e);
    sum = a + b + c + d + e;
    printf("%.2lf", sum / 5);
    return 0;
}